Patent law has a significant instrumental and symbolic role in regulating nanotechnology. A 2011 report of the United States Federal Trade Commission noted that ‘the patent system plays a critical role in promoting innovation across industries from biotechnology to nanotechnology, and by entities from large corporations to independent inventors’. This chapter considers the much contested legal, ethical and social issues involved with regulating the patenting of nanotechnology. Section I considers the efforts of patent offices to classify nanotechnology and the empirical evidence about patent filing rates. Section II examines whether there is a ‘tragedy of the anticommons’ emerging in respect of nanotechnology. It contemplates access mechanisms – such as the defence of experimental use, patent pools, open innovation models and technology transfer. Section III explores ethical and social concerns associated with nanotechnology – in particular, issues about the impact upon human health and the environment.